1. Field of the Invention
The present invention relates generally to valve assemblies, and in particular to a valve assembly with a head-guided, stemless poppet valve member.
2. Description of the Prior Art
Fluid pumps and compressors commonly include suction valves for fluid intake and discharge valves for fluid exhaust. In reciprocating-type pumps and compressors the valve assemblies are automatically actuated by the changing fluid pressure differential across them. On a suction stroke the compressor or pump piston is moving away from a suction valve assembly located at one end of the compressor cylinder. As the volume of the compressor cylinder thus expands, its pressure decreases to a point where a greater fluid pressure in a suction line causes the suction valve assembly to open and refill the compressor cylinder with pressurized fluid.
On a discharge stroke the piston contracts the cylinder volume, thereby increasing the fluid pressure until the discharge valve assembly opens under the influence of a pressure differential across it. The suction and discharge valve assemblies generally permit fluid flow in one direction only and automatically close when the fluid pressure differential drops below the predetermined level necessary to hold the valve assembly open.
Many reciprocating-type pumps and compressors are of the double-acting type wherein each cylinder end has one or more suction valve assemblies and one or more discharge valve assemblies. Thus, the piston discharge stroke at one end of the compressor cylinder is the suction stroke at the other end and vice versa. For example, such double-acting reciprocating compressors are typically provided in pumping stations along natural gas pipelines which transport large quantities of natural gas. Efficient transportation of natural gas through pipelines is highly dependent upon the efficiency of the compressors, which in turn depends upon a number of factors, including the efficiency of the valve assemblies.
Automatic-lift, one-way valve assemblies include valve members that selectively engage seats to close the seat fluid passages therethrough. Valve members heretofore employed include plates, channels, reeds and poppets. Poppet valve members generally include heads with convex or frusto-conical mating surfaces for engaging corresponding valve seats. Most prior art poppet valve members also include guide stems extending from their heads in a downstream direction. For example, the Bunn et al. U.S. Pat. No. 3,701,361 discloses a poppet valve member with a guide stem extending in a downstream direction from a head and a plurality of fins extending in an upstream direction from the head. The fins are slidably received in a port extending through a valve seat. Both the guide stem and the fins guide the valve member in reciprocation between its open and closed positions.
However, a disadvantage with this and many other prior art poppet valve assemblies is that they require cages with relatively high profiles to receive the valve member stems. Such higher profiles and greater overall valve assembly depth can contribute to lower compressor efficiencies because they tend to add clearance volume at the compressor ends. Accordingly, it is desirable to provide valve assemblies with profiles that are as low as possible so that minimal clearance is added to the compressor ends. The present invention addresses this problem. Heretofore, there has not been available a valve assembly or valve member with the advantages and features of the present invention.